On One Fatty Sizing

I have been thinking about building up a On One Fatty for my wife, but I wondering about the sizing. She is about 5'5" and I'm wondering if the 16" frame is going to be too big for her. It appears that the geometry is very close to a small Mukluk and that fits her fine. I think that the stand over might be taller on the Fatty. Is there anyone out there around 5'5" that can give me there thoughts on the fit? Thanks!